Superallowed Fermi Beta Decay Studies at TRIUMF-ISAC C.E. Svensson, University o Guelph CAP Congress, Sudbury, Ontario June 16 – 20, 2014
Feb 23, 2016
Superallowed Fermi Beta
Decay Studies at TRIUMF-
ISACC.E. Svensson, University of Guelph
CAP Congress, Sudbury, OntarioJune 16 – 20, 2014
The Cabibbo-Kobayashi-Maskawa (CKM) matrixThe CKM matrix plays a central role in the Standard
Model and underpins all quark flavour-changing interactions: weak interaction eigenstates quark mass eigenstates
In the Standard Model the CKM describes a unitary transformation.
bsd
VVVVVVVVV
'b's'd
tbtstd
cbcscd
ubusud
1222 ubusud VVV
The first row of the CKM matrix provides, by far, the most demanding experimental test of this unitarity condition.
du
ne
e-W-
gg
bVsVdVd ubusud
CKM Unitarity
Series10.000.100.200.300.400.500.600.700.800.901.00
0.97425 (22)
0.2256(8) 0.00415
(49)
Vud Vus Vub
J.C. Hardy and I.S. Towner, Ann. Phys. (Berlin) 525, 443 (2013).
0.90 0.92 0.94 0.96 0.98 1.00
Vud Vus Vub
|Vud|2 + |Vus|2 + |Vub|2 = 1.00008(43)Vud(36)Vus
…
CKM Unitarity
J.C. Hardy and I.S. Towner, Ann. Phys. (Berlin) 525, 443 (2013).
R.J. Dowdall et al., Phys. Rev. D 88, 074504 (2013)
K+ → ln / p+ → ln (HPQCD Collaboration)
|Vus| = 0.22564(53)
In the Standard Model the CKM describes a unitary transformation.
New Lattice QCD Form Factor Calculations for Vus
|Vud|2 + |Vus|2 + |Vub|2 = 1.00009(43)Vud(24)VusA. Bazavov et al., Phys. Rev. Lett. 112, 112001
(2014)K+ → p+ln (Fermilab Lattice and MILC
Collaborations)
|Vus| = 0.22290(90)
In the Standard Model the CKM describes a unitary transformation.
|Vud|2 + |Vus|2 + |Vub|2 = 0.99885(43)Vud(40)Vus
To first order, b decay ft values can be expressed as:
f t = K|Mfi|2 g2
constants
Weak couplingstrength
phase space (Q-value)
half-life, branching ratio
For the special case of 0+ 0+ (pure Fermi) b decays between isobaric analogue states (superallowed) the matrix element isthat of an isospin ladder operator: |Mfi|2 = (T – TZ)(T + TZ + 1) = 2 (for T=1)
Strategy: Measure superallowed ft-values, deduce GV and Vud:K
2 ftGV
2 = |Vud| = GV / GF
matrix element
Vector couplingconstant
Fermi couplingconstant
Vud from Superallowed Fermi b Decay
b decay ft-values
Superallowed ft-values
2%
ft ≈ K2 Gv
2= constant (CVC)
Superallowed Fermi b Decay: Corrections
Calculated corrections (~1%) (nucleus dependent)
Inner radiative correction (~2.4%) (nucleus independent)Experiment
CVC Hypothesis
constant12
δδ1δ1 VR
2V
CNSR
-GKftFtFt
“Corrected” ft value
R = nucleus independent inner radiative correction: 2.361(38)%
dR = nucleus dependent radiative correction to order Z2a3: ~1.4%
- depends on electron’s energy and Z of nucleusdNS = nuclear structure dependent radiative correction: -0.3% – 0.03%dC = nucleus dependent isospin-symmetry-breaking correction: 0.2% – 1.5%
- strong nuclear structure dependence
V
Corrected Superallowed Ft Values
FtWS = 3072.38(75)χ2/ν =
0.32
P. Finlay, et al., Phys. Rev. Lett. 106, 032501 (2011)R. Dunlop, et al., Phys. Rev. C 88, 045501 (2013)
Theoretical Treatment of δC
Many recent approaches to
ISB corrections→ Nuclear Shell Model→ Relativistic Hartree-Fock→ Random Phase Approximation→ Energy Density Functional
Difference between Woods-Saxon and Hartree-Fock Radial Overlap
Corrections
TRIUMF-ISACUp to 100 mA, 500 MeV proton beams from the TRIUMF main cyclotron produce high-intensity secondary beams of many of the superallowed emitters by the ISOL technique.
Superallowed Fermi b Decay Studies at ISAC
Halflives (GPS) Branching ratios (8p)
Masses (TITAN)
Charge Radii (laser spectroscopy)Near Future (GRIFFIN)
Halflives (ZDS)
46V
66As70Br
74Rb
N=Z
line
18Ne
34Ar38m
K
26mAl
50Mn
14O10C T½ by β and γ
counting M. Dunlop et al.
T½, G.F. Grinyer et al, PRC 76, 025503 (2007) PRC 87, 045502 (2013)
BR, K.G. Leach et al., PRL 100, 192504 (2008) T1/2 , G.C. Ball et al, PRC 82, 045501 (2010)
T½ and BR
{T½ and BR
62Ga
T½, G.F. Grinyer, PRC 77, 201501 (2008) BR, B.H. Hyland, PRL 97, 102501 (2006)BR, P. Finlay PRC 78, 044321 (2008)
T1/2 , G.C. Ball et al, PRL 86 1454 (2001)BR, A. Piechaczek et al, PRC 67, 051305 (2003)BR, R. Dunlop et al, PRC 88, 045501 (2013)Q: S. Ettenauer et al., PRL 107, 272501 (2011)CR: E. Mané et al, PRL 107, 212502 (2011)
T½ P. Finlay et al, PRL 106, 032501 (2011)BR, P. Finlay et al, PRC 85, 055501 (2012)
Superallowed b Decay
Studies at ISAC
54Co
T½, A.T. Laffoley et al, PRC 88, 015501 (2013)
14O Half-Life MeasurementSimultaneous independent direct β and γ-ray counting experiments using the 8π spectrometer and the Zero-Degree Scintillator.γ Counting: -Decay Selective-Slow & Inefficientβ Counting: -Fast & Efficient-Not Decay Selective
Previous measurements reveal a systematic discrepancy between detection method
14O Half-Life vs Detection Method
12C-14O: T1/2 = 70.620 s 26Alm: T1/2 = 6.3465 s26Na: T1/2 = 1.072 s
Beam
14O Half-Life Measurement at ISAC
b Counting
g Counting
β
γ
14O Half-Life
Initial experiment shows consistency between β and γ half-life measurements for 14O.
A follow-up experiment is scheduled for July, 2014 to push to 0.01% precision.
ft measurements for light superallowed Fermi β emitters are required to constrain scalar currents in the weak interaction.
A.T. Laffoley et al., Phys. Rev. C 88, 015501 (2013)
18Ne Superallowed Decay18Ne 0+T = 1T½ = 1.6654(11) sQ = 4443.6 keV
β+
β+
β+
18F
1+ 1701 0.19%
1+ 0 92.11%
0- 1081 0.0002%0+ 1042 7.70%
β+
18O 0+
T = 0
T = 1 stable
T½ = 109.73(2) minQ = 1655.5 keV
T = 1T = 1
4π Gas Counter and Thick Tape Transport
4π continuous-flow gas-proportional counter and tape transport system
Methane (CH4) gas ~ 100% efficient β counter Very low background rates
28 cm
E. F. Zganjar
18Ne Sample Data – Gas Counter
Status of 18Ne Half-life
Half-life precision improved by a factor of 3, to 0.025%
Preliminary
74Rb Superallowed Decay (T1/2 ~ 65 ms)
Halflife: Measured with the GPS 4p gas proportional counter at ISAC.
T1/2 = 64.761(31) ms G.C. Ball et al., Phys. Rev. Lett. 86, 1454 (2001).Mass: First demonstration of a high charge state mass measurement for a short-lived isotope with the TITAN Penning trap.
S. Ettenauer et al., Phys. Rev. Lett. 107, 272501 (2011).Charge Radius: Measured via collinear laser spectroscopy:
<r2ch>1/2 = 4.19(1) fm
Reduces uncertainty in theoretical dC2 by ~ 20%
E. Mané et al., Phys. Rev. Lett. 107, 212502 (2011).Branching Ratio: Measured with the 8p Spectrometer to ± 0.03% BR = 99.545 (31) % R. Dunlop et al., Phys. Rev. C 88, 045501 (2013).
Superallowed b Branching Ratios for A ≥ 62 and the Pandemonium
Effect
For large Q-value b decays, there are generally many weak b branches to the large number of daughter states within the Q-value window.
In the subsequent g decay, many individual g-rays may be too weak to identify.
The sum of these unobserved g intensities will, however, generally be sufficient to prevent precision determination of b decay branching ratios through g-ray spectroscopy.
8p Spectrometer – Decay Spectroscopy at ISAC-I
Simultaneous collection of g-singles, gg coincidences, b tagging, conversion electrons, and lifetime measurements
Counting 74Rb b Decays with SCEPTAR
Identifying g-rays from 74Rb Decay
Raw γ-spectrum contains lines from room
background and in-beam contaminants
β-γ coincidence, Bremsstralung
suppression reduce background
Spectrum during beam-off allows one to
identify long-lived contaminants
g-g Coincidences following ppm b-decay branches of 74Rb
Internal Conversion Decay of the 0+2
State of 74Kr b - g - electron Coincidence Spectrum
57 g-ray transitions identified following 74Rb decay
Ground-state g-feeding of Igs = 3950(70) ppm identified.
Controlling Pandemonium via 2+ “Collector” States
~ 400 1+ LevelsI'gs
I'2+
I'2+ = 1225(57) ppmBgs = I'gs /(I'gs + I'2+)
Expt + Shell Model:Bgs = 0.33(11)
I'gs = 600(300) ppm
Superallowed Branching Ratio:99.545 ± 0.031 %
Direct b feeding of 2+ states is negligible
R. Dunlop PRC 88, 045501 (2013)
Igs = 3950(70) ppm
74Rb Superallowed Decay
74Rb Superallowed Error Budget
The Future …GammaRayInfrastructureForFundamentalInvestigations of
NucleiA new high-efficiency decay spectroscopy facility for ISAC-I
GRIFFIN @ ISAC-I
June 14, 2014
GRIFFIN
17 times the efficiency of the 8π at Eg = 1 MeV
Efficiency improvement increases with g-ray energy
38
16 large-volume clover-type HPGe g-ray detector
~300x the γ-γ efficiency of the 8π Geant4
74Rb Superallowed Decay with GRIFFIN
Angular Correlation Measurements with GRIFIFN
(S1518: 62Ga superallowed decay)
Using GRIFFIN we can determine the spin-parity of the 2342 keV state
0.00+
9542+
2342
E2
0+
E22+
M1+E2
Geant4 40
World Superallowed Fermi b Decay Data
Ft = 3072.35(75)s c2/n = 0.31
World Superallowed Fermi b Decay DataCVC hypothesis confirmed to ± 0.013%
Set limits on maximally parity violating weak scalar currents:
CS/CV = 0.0011 ± 0.0013
Vud determined from the superallowed data is, by far, the most preciselydetermined element of the CKM quark-mixing matrix:
|Vud| = 0.97425 ± 0.00022
and together with Vus (and Vub) provides the most demanding experimental test of the unitarity of the CKM matrix:
|Vud|2 + |Vus|2 + |Vub|2 = 1.00008 ± 0.00056
Model-dependence of the strongly nuclear structure dependent isospin symmetry breaking corrections in superallowed Fermi b decays remains a key focus of research for both the theoretical and experimental communities.
V. BildsteinG. DengA. Diaz VarelaM. DunlopR. DunlopZ. FairchildP. E. GarrettB. HadiniaD. S. JamiesonB. JigmeddorjA.T. LaffoleyA. RadichE. T. RandC. E. Svensson
G. C. BallP. C. BenderT. BruhnA. B. GarnsworthyG. HackmanS. KetelhutK. G. LeachB. MillsM. MoukaddamM. M. RajabaliE. TardiffC. Unsworth
C. AndreoiuD. S. CrossP. Voss K. Starosta
R. A. E. Austin
H. BouzomitaG. F. GrinyerJ. C. Thomas
J. R. Leslie
E. F. Zganjar
B. BlankJ. Giovinazzo
P. Finlay
I.S. Towner
46V
66As70Br
74Rb
N=Z
line
18Ne
34Ar38m
K
26mAl
50Mn
14O10C T½ by β and γ
counting M. Dunlop et al.
T½, G.F. Grinyer et al, PRC 76, 025503 (2007) PRC 87, 045502 (2013)
BR, K.G. Leach et al., PRL 100, 192504 (2008) T1/2 , G.C. Ball et al, PRC 82, 045501 (2010)
T½ and BR
{T½ and BR
62Ga
T½, G.F. Grinyer, PRC 77, 201501 (2008) BR, B.H. Hyland, PRL 97, 102501 (2006)BR, P. Finlay PRC 78, 044321 (2008)
T1/2 , G.C. Ball et al, PRL 86 1454 (2001)BR, A. Piechaczek et al, PRC 67, 051305 (2003)BR, R. Dunlop et al, PRC 88, 045501 (2013)Q: S. Ettenauer et al., PRL 107, 272501 (2011)CR: E. Mané et al, PRL 107, 212502 (2011)
T½ P. Finlay et al, PRL 106, 032501 (2011)BR, P. Finlay et al, PRC 85, 055501 (2012)
Superallowed b Decay
Studies at ISAC
54Co
T½, A.T. Laffoley et al, PRC 88, 015501 (2013)